I'm developing a game with procedurally generated dungeons with a somewhat minecrafty spirit (But 2D), and it's time for the inventory. I've never programmed an inventory before, so I'm figuring out how to do it by my own.

Here's my humble inventory with a humble item at a random position:

The first thing that came to my mind when I faced the necessity of creating an inventory, was, naturally: "A list!" (Python). So, here's the code of my Inventory class:

class Inventory(ImageEntity):
def __init__(self,filename):
ImageEntity.__init__(self,"GFX",filename,0,0)
self.interface = gIBGI(filename)
self.cursor = InterfaceSelectionCursor("GFX","selectionCursor.png",0,0)
self.slots = []
for i in range(8):
self.slots.append([])
for j in range(8):
self.slots[i].append([0,"No hotkey",(j*interfaceWidth,i*interfaceHeight)])
ew0InitialPos = (randint(0,7),randint(0,7))
ew0.x = self.getInterfaceX(ew0InitialPos[0])
ew0.y = self.getInterfaceY(ew0InitialPos[1])
self.slots[ew0InitialPos[0]][ew0InitialPos[1]][0] = ew0
self.slotHolder = 0
self.itemSelectedByMouse = False
def watchForHotkeyAssignments(self):
for i in self.slots:
for slot in i:
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_1] or key.get_pressed()[K_KP1])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 1"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_2] or key.get_pressed()[K_KP2])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 2"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_3] or key.get_pressed()[K_KP3])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 3"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_4] or key.get_pressed()[K_KP4])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 4"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_5] or key.get_pressed()[K_KP5])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 5"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_6] or key.get_pressed()[K_KP6])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 6"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_7] or key.get_pressed()[K_KP7])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 7"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_8] or key.get_pressed()[K_KP8])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 8"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_9] or key.get_pressed()[K_KP9])):
if slot[2] == (self.cursor.x,self.cursor.y):
slot[1] = "Hotkey 9"
def watchForPositionalMouseRequests(self):
for i in self.slots:
for slot in i:
if mouse.get_pressed()[0]:
if slot[2] == (self.cursor.x,self.cursor.y):
if slot[0] != 0:
pass
# At this point it iterates over all the slots (Which are filled with 0 by default.)
# If the slot[0] is equal to an item, then, I can access its x and y position (Set it to the cursor pos, for example).
if mouse.get_pressed()[0] == False:
if slot[2] == (self.cursor.x,self.cursor.y):
pass # Do something when mouse button 1 released.
def draw(self):
screen.blit(self.interface,(0,0))
self.cursor.draw("INTERFACE")
self.cursor.move()
for i in self.slots:
for slot in i:
if slot[0] != 0:
slot[0].draw("INTERFACE")

Interface width and height are 128 by 96 (The size of each tile, including the item and cursor (They are transformed for the inventory screen)). As you can see, I figured out how to assign hotkeys for each slot (A vital necessity in the game I'm developing). Nevertheless, I would like to move the item to a new slot when clicked.

How would you do that? I know how to filter the slot (I mean, when I click, I know how to capture the Item, which is an image-object with a x and y position). Things get weird when I try to make the item's x and y positions the position of the selection cursor, considering that I access it only when I filter to the first slot that was clicked (Therefore, if I move the item, I cannot move it again and things get pretty confusing).

Anyway, I would like to know how a more experienced programmer would deal with this problem. I thank you very much!

Edited by EricsonWillians, 27 May 2014 - 01:01 PM.

Creator and only composer at Poisone Wein and Übelkraft dark musical projects:

What are `interfaceWidth` and `interfaceHeight`? Are they the width/height of each slot, or of the entire user interface? (If I'm reading right, they're being used as slot width/height. If that's correct, you should consider renaming these variables.)

The logic in `watchForHotkeyAssignments` could be simplified a lot. For example, `key.get_pressed()[K_LCTRL]` and `slot[2]==(self.cursor.x,self.cursor.y)` only need to be checked once in side the loop. How could you simplify the logic?

I think it's best to separate the _functionality_ as much as possible from the _presentation/UI_. For example, your data structure (the 2d list) `slots` contains information about the screen coordinates/pixels. Can you separate these somehow? Ideally, `slots` would just contain inventory data, and the Inventory class would have methods for performing certain actions (selectItem, moveItem, assignHotkey, etc.). Then you could have a method which will translate mouse cursor coordinates into slot coordinates.

I thank you very much for your answer. I've managed to solve the problem. It was really difficult, and probably because of my structure. Nonetheless, I've increassed the code's complexity. Now I'm using hashmaps/dictionaries for the slots (A storage-dictionary whose keys are tuple-positions, whose values are lists with two indexes: One for the item, other for the hotkey). I've commented the code step by step, and I'll post here so that you can see what I've done. As soon as I finish the game, I'll announce it here on Gamedev.

class Inventory(ImageEntity):
def __init__(self,filename):
ImageEntity.__init__(self,"GFX",filename,0,0)
self.interface = gIBGI(filename)
self.cursor = InterfaceSelectionCursor("GFX","selectionCursor.png",0,0)
self.storage = GridMap(interfaceGrid) # A GridMap is a dictionary-custom-class with all possible positions within a grid as keys.
for slot in self.storage: # Iterates through that empty dictionary with all the key-positions with empty values.
self.storage[slot] = [0,"No hotkey"] # Assigns a default value to them (No item and no hotkey, inside a list).
# Generate random starting-positions for the starting-item in the inventory.
ew0InitialPos = (randint(0,7),randint(0,7))
ew0.x = self.getInterfaceX(ew0InitialPos[0])
ew0.y = self.getInterfaceY(ew0InitialPos[1])
self.storage[(ew0InitialPos[0],ew0InitialPos[1])][0] = ew0
self.isItemSelected = False # Necessary to move the item in real time through the slots.
self.slotHolder = None # Necessary to transfer the item-object from the mouse-down loop to the mouse-up loop.
self.slotToBeErased = None # Necessary to erase the previous item in order not to allow copies to be accidentally made.
def watchForPositionalMouseRequests(self):
# Iterates over the event list.
for e in event.get():
# Checks if the mouse button 1 was pressed.
if e.type == MOUSEBUTTONDOWN and mouse.get_pressed()[0] == True:
# Checks if no item is already selected.
if self.isItemSelected == False:
# Iterates over the storage dictionary (All the slots,
# which are lists with 2 indexes: One for a possible item and other for a possible hotkey).
for slot in self.storage:
# Filters the slot specifically under the mouse selection cursor (The one that shall be used).
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
# Checks whether that slot under the mouse cursor has an item object or not.
if isinstance(self.storage[slot][0],Item): # If it has, then it is an instance of the Item class.
# If all those conditions are true, then, the item is finally selected.
self.isItemSelected = True
# Checks if there's no previous item in the slotholder.
if self.slotHolder is None:
# Changes the drawing-positions of the item, but does not update them in real time.
self.storage[slot][0].x = self.cursor.x
self.storage[slot][0].y = self.cursor.y
# Copies the item to the slotholder.
self.slotHolder = self.storage[slot][0]
# Copies the slot that was initially clicked just
# to keep track of it through the loops in order to erase it in the next one.
self.slotToBeErased = slot
# Checks if the mouse button 1 was released.
if e.type == MOUSEBUTTONUP and mouse.get_pressed()[0] == False:
# Guarantees that an item is indeed selected when the mouse button is released.
if self.isItemSelected == True:
# Iterates over the storage dictionary again, separately.
for slot in list(self.storage):
# Filters the slot specifically under the mouse selection cursor, again
# (But this is the new slot, which is the item's destination.)
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
# Checks if there is an item in the slotholder from the previous loop.
if self.slotHolder is not None:
# If all those conditions are true, then, there's really an item selected and
# it certainlly is that one that was firstly clicked to be moved.
# Then, since the mouse was now released, the item can be "dropped" to its final destination.
self.isItemSelected = False
self.storage[slot][0] = self.slotHolder
self.slotHolder = None
if self.slotToBeErased is not None:
if slot != self.slotToBeErased:
self.storage[self.slotToBeErased][0] = 0
self.slotToBeErased = None
def draw(self):
screen.blit(self.interface,(0,0))
self.cursor.draw("INTERFACE")
self.cursor.move()
for slot in self.storage:
try:
if isinstance(self.storage[slot][0],Item):
if self.isItemSelected == True:
self.storage[slot][0].x = self.cursor.x
self.storage[slot][0].y = self.cursor.y
self.storage[slot][0].draw("INTERFACE")
for n in range(1,10,1):
if str(n) in self.storage[slot][1]:
gPT([str(n),self.storage[slot][0].x,self.storage[slot][0].y],
[str(n),self.storage[slot][0].x,self.storage[slot][0].y],(255,255,255),32)
except:
pass
if self.slotHolder is not None:
self.slotHolder.draw("INTERFACE")
def watchForHotkeyAssignments(self):
for slot in self.storage:
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_0] or key.get_pressed()[K_KP0])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "No hotkey"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_1] or key.get_pressed()[K_KP1])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 1"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_2] or key.get_pressed()[K_KP2])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 2"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_3] or key.get_pressed()[K_KP3])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 3"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_4] or key.get_pressed()[K_KP4])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 4"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_5] or key.get_pressed()[K_KP5])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 5"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_6] or key.get_pressed()[K_KP6])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 6"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_7] or key.get_pressed()[K_KP7])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 7"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_8] or key.get_pressed()[K_KP8])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 8"
if (key.get_pressed()[K_LCTRL] and (key.get_pressed()[K_9] or key.get_pressed()[K_KP9])):
if (self.getInterfaceX(slot[0]),self.getInterfaceY(slot[1])) == (self.cursor.x,self.cursor.y):
self.storage[slot][1] = "Hotkey 9"

Creator and only composer at Poisone Wein and Übelkraft dark musical projects:

You probably should seriously reconsider your code design if you need a comment on every line or every few lines explaining what each thing is doing. Even if your code is meant to be a tutorial or something its a little overboard.

The only time you should really have to use comments in code is to explain -intent- of something rather than trying to write out what an actual line of code is doing. It makes a lot more sense to explain that a couple lines of code are a safeguard against potential hacks than it does to write a couple lines of comments explaining that line 27 puts some object into a list for some reason and then line 29 loops through it looking for some character you don't want, or whatever your case may be.

I recently commented on a similar topic to this about inventory in a game, as was stated above the presentation should really be seperate from the data, thats a concept that is very common in game development. Pretty much everything can be split up into: receive input, do logic, present results.